Insulator material for use in RRAM

ABSTRACT

The present disclosure relates generally to Hf-comprising materials for use in, for example, the insulator of a RRAM device, and to methods for making such materials. In one aspect, the disclosure provides a method for the manufacture of a layer of material over a substrate, said method including
         a) providing a substrate, and   b) depositing a layer of material on said substrate via ALD at a temperature of from 250 to 500° C., said depositing step comprising:
           at least one HfX 4  pulse, and   at least one trimethyl-aluminum (TMA) pulse,   
               

     wherein X is a halogen selected from Cl, Br, I and F and is preferably Cl.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of European pat. app.no. 12179378.0 filed on Aug. 6, 2012, which is hereby incorporatedherein by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates to a Hf-comprising material for use inthe insulator of a RRAM device.

BACKGROUND ART

Resistive random-access memory (RRAM) is a non-volatile memory typeunder development. RRAM has recently gained much interest as a potentialreplacement for FLASH memory.

The basic idea is that a dielectric, which is normally insulating, canbe made to conduct through a filament or conduction path formed afterapplication of a sufficiently high voltage. The conduction pathformation can arise from different mechanisms, including defects, metalmigration, etc. Once the filament is formed, it may be reset (broken,resulting in high resistance) or set (re-formed, resulting in lowerresistance) by an appropriately applied voltage.

At the basis of RRAM is a metal-insulator-metal (MIM) stack. HfO₂ hasbeen of great interest as the insulator in the MIM stack. However, abetter performance has been demonstrated by not only using HfO₂ as theinsulator but by using a bi-layer of a stoichiometric HfO₂ layer and anon-stoichiometric O-deficient HfOx (x<2) layer. For HfO₂, the commonlyaccepted mechanism of filament creation and destruction occurs by thediffusion of oxygen vacancies. Oxygen vacancies lead to defect states inthe HfO₂ dielectric; if a large number of oxygen vacancies are present(locally), the HfO₂ dielectric becomes conductive. In such a bilayerstack, the non-stoichiometric O-deficient HfOx (x<2) layer can act as asink for oxygen. So far, this O-deficient HfOx layer has always beendeposited by PVD but for integration, it would be of great interest todeposit the layer by ALD, which is more manufacturing friendly and whichis the method typically used for HfO₂ deposition. A general descriptionof ALD is disclosed in [0004] to [0009] of US2005/0227003. So far, anALD process for HfOx with x<2 has been elusive since no stable phaseother than HfO₂ exists in the Hf—O phase diagram and the deposition ofsuboxides by ALD is generally difficult. There is therefore a need inthe art for an alternative material which can be deposited by ALD.

SUMMARY OF THE DISCLOSURE

In certain aspects, the present disclosure provides an alternative tothe PVD deposited O-deficient HfOx material, which can be deposited byALD. This aspect can be achieved according to the disclosure with thematerials as described herein.

In other aspects, the present disclosure provides a method for formingsaid material on a substrate. This aspect can be achieved according tothe disclosure with the methods as described herein.

Herein is disclosed an ALD method leading to the fabrication ofmaterials and in particular oxygen-deficient materials that can be usedin combination with a HfO₂ layer to form the insulator of a MIM stack,advantageous for use in RRAM applications.

In a first aspect, the present disclosure relates to a method for themanufacture of a layer of material over a substrate, said methodcomprising

a) providing a substrate, and

b) depositing a layer of material on said substrate via ALD at atemperature of from 250 to 500° C., said depositing step comprising:

-   -   at least one HfX₄ pulse, and    -   at least one trimethyl-aluminum (TMA) pulse,

wherein X is a halogen selected from Cl, Br, I and F and is preferablyCl.

In an embodiment, said HfX₄ pulse may be performed before said TMApulse.

In an embodiment, the method may further comprise at least one oxidizer(Ox) pulse.

In an embodiment, said oxidizer pulse may be selected from H₂O and O₃pulses.

In an embodiment, said depositing step may comprise any one of thefollowing sequence of pulses:

-   -   HfX₄/TMA/optionally repeated one or more times, or    -   HfX₄/TMA/Ox/optionally repeated one or more times, or    -   HfX₄/Ox/TMA/optionally repeated one or more times.

In an embodiment, said depositing step may comprise any one of thefollowing sequence of pulses or a combination thereof:

-   -   (HfX₄/TMA/)_(n1)(HfX₄/Ox/)_(m1), or    -   (HfX₄/TMA/Ox/)_(n2)(HfX₄/Ox/)_(m2), or    -   (HfX₄/Ox/TMA/)_(n3)(HfX₄)Ox/)_(m3).

-   Wherein n1 is from 1 to 300, preferably from 1 to 50 and more    preferably from 1 to 15,

-   Wherein n2 is from 1 to 500, preferably from 1 to 50 and more    preferably from 1 to 15,

-   Wherein n3 is from 1 to 500, preferably from 1 to 50 and more    preferably from 1 to 15,

-   Wherein m1, m2 and m3 are from 0 to 100, preferably from 0 to 30.

In embodiments where the deposition step comprises a combination of twoor more of the above sequences, the sum of all n1, n2, n3, m1, m2, andm3 is preferably not more than 1000. As an example, for the followingsequence {[(HfX₄/TMA/)₁₀(HfX₄/Ox/)₅]₂(HfX₄/Ox/TMA/)₃}₅, said sum wouldamount to ((10+5)*2+3)*5=165 which is not more than 1000.

The notation A/B/ is shorthand for A pulse-purge-B pulse-purge.

Purging may involve a variety of techniques including, but not limitedto, contacting the substrate and/or monolayer with an inert gas and/orlowering pressure to below the deposition pressure to reduce theconcentration of a species contacting the substrate and/or chemisorbedspecies. Examples of inert gases include N₂, Ar, He, Ne, Kr, Xe, etc.Purging may instead include contacting the substrate and/or monolayerwith any substance that allows chemisorption by-products to desorb andreduces the concentration of a species preparatory to introducinganother species. A suitable amount of purging can be determinedexperimentally as known to those skilled in the art. Purging time may besuccessively reduced to a purge time that yields an increase in filmgrowth rate. The increase in film growth rate might be an indication ofa change to a non-ALD process regime and may be used to establish apurge time limit.

Preferably, N₂ is used for purging.

In embodiments, the method may further comprise the step of providing aHfO₂ layer directly above or below said layer of material.

In embodiments, said HfO₂ layer may be provided by a sequence of pcycles of the sequence HfX₄/Ox/.

In an embodiment, said depositing step may comprise any one of thefollowing sequence of pulses or a combination thereof:

-   -   (HfX₄/TMA/)_(n1)(HfX₄/Ox/)_(m1), or    -   (HfX₄/TMA/Ox/)_(n2)(HfX₄/Ox/)_(m2), or    -   (HfX₄/Ox/TMA/)_(n3)(HfX₄/Ox/)_(m3).

followed (or preceded) by the provision of a HfO₂ layer via thefollowing sequence of pulses (HfX₄/Ox/)_(p),

wherein p is from 1 to 100 and preferably from 1 to 30.

In embodiments, X may be Cl.

In embodiments, said temperature may be from 300 to 400° C., preferablyfrom 340 to 380° C., more preferably from 340 to 370° C. This isadvantageous because higher temperature introduces a disadvantageous CVDcomponent in the TMA ALD process and because lower temperature provideinexistent or negligible layer formation. In an embodiment, saidtemperature is the temperature of the substrate.

In an embodiment, the thickness of said layer of material may be from0.3 to 100 nm.

In a second aspect, the present disclosure relates to a materialcomprising the elements Hf, Al and optionally C and/or O and/or X,wherein said material comprises at least the element C or O, wherein Xis selected from Cl, Br, I and F (preferably Cl), wherein said elementsmakes up at least 90% of the at % (i.e., atomic percent) composition ofthe material as determined by XPS (and therefore ignoring the hydrogencontent), wherein Hf represents from 17 to 40 at % of said elements(i.e. Hf, Al, C, O and X), Al represents from 5 to 23 at % of saidelements, C represents from 0 to 45 at % of said elements, O representsfrom 0 to 62% of said elements, X represents from 0 to 10 at % of saidelements, the sum of said elements amounting to 100 at %. In anembodiment, said elements Hf, Al and optionally C and/or O and/or X maymake up at least 93%, preferably at least 96% and most preferably atleast 99% of the at % composition of the material as determined by XPS.

These proportions in Hf, Al, C, O and X can be tuned by varying theproportion of sequences comprising an oxidative pulse. A higherproportion of sequences comprising an oxidative pulse leads to a lowerHf content, a lower C content, a higher Al content, a higher O content,and a lower X content.

It is worth noting that XPS analysis does not determine the hydrogencontent of a sample. Of course, other elements than Hf, Al, C, O and Xcan be present in the composition as determined by XPS as long as theyare not present in such an amount as to diminish the proportionrepresented by Hf, Al, C, O and X below 90%, preferably below 93%, morepreferably below 96% and most preferably below 99% of the at %composition of the material as determined by XPS.

In embodiments, said material comprising the elements Hf, Al andoptionally C and/or O and/or X, wherein said material comprises at leastthe element C or O, may further comprise from 0 to 20 at % of hydrogenas determined by Time-of-Flight Elastic Recoil detection analysis(TOF-ERDA). This value can be tuned by varying the proportion ofsequences comprising an oxidative pulse. A higher proportion ofsequences comprising an oxidative pulse leads to a lower hydrogencontent.

In embodiments of the second aspect, the band gap of the material may beanywhere from 0 to about 6.5 eV. This value can be tuned by varying theproportion of sequences comprising an oxidative pulse. A higherproportion of sequences comprising an oxidative pulse leads to a largerband gap.

The material of the second aspect may be produced by the method of thefirst aspect.

In a first embodiment of the second aspect,

-   -   Hf may represent from 29 to 40 at % of said elements Hf, Al, C,        O and X as measured by XPS,    -   Al may represent from 5 to 15 at % of said elements Hf, Al, C, O        and X as measured by XPS;    -   C may represent from 31 to 45 at % of said elements Hf, Al, C, O        and X as measured by XPS;    -   O may represent from 0 to 14 at % of said elements Hf, Al, C, O        and X as measured by XPS;    -   X may represent from 0 to 10 at % of said elements Hf, Al, C, O        and X as measured by XPS,    -   the sum of said elements amounting to 100 at %,

In this first embodiment, said material may further comprise from 5 to20 at % of hydrogen as determined by Time-of-Flight Elastic Recoildetection analysis (TOF-ERDA).

For instance, the first embodiment of the second aspect of the presentdisclosure may relate to a material comprising the elements Hf, C, Al, Oand X, wherein said elements make up at least 90% (preferably at least94, more preferably at least 96 and most preferably at least 99%) of theat % composition of the material as determined by XPS, wherein Hfrepresents from 34 to 40 at % of said elements (i.e. of Hf, C, Al, O andX), C represents from 36 to 45 at % and preferably 40 to 45 at % of saidelements, Al represents from 9 to 14 at % of said elements, O representsfrom 0 to 9 at % and preferably from 0 to 6 at % of said elements and Xrepresents 2 to 9 at % and preferably from 2 to 6 at % of said elements,the sum of said at % of said elements amounting to 100 at %, wherein Xis a halogen selected from Cl, Br, I and F and is preferably Cl.

In the first embodiment of the second aspect, said material may beelectrically conductive (i.e. behaving as a metal).

The material of the first embodiment of the second aspect may beproduced by the method of the first aspect wherein no oxidizer pulse isused, i.e. wherein the sequence of pulse is (HfX₄/TMA)_(n1).

In a second embodiment of the second aspect,

-   -   Hf may represent from 17 to 23 at % of said elements Hf, Al, C,        O and X as measured by XPS;    -   Al may represent from 16 to 23 at % of said elements Hf, Al, C,        O and X as measured by XPS;    -   O may represent 57 to 62 at % of said elements Hf, Al, C, O and        X as measured by XPS;    -   C may represent from 0 to 3 at % of said elements Hf, Al, C, O        and X as measured by XPS;    -   X may represent from 0 to 1% of said elements Hf, Al, C, O and X        as measured by XPS;    -   the sum of said at % of said elements amounting to 100 at %.

The material of the second embodiment of the second aspect may beproduced by the method of the first aspect wherein an oxidizer pulse isused in each sequence, e.g. wherein the sequence of pulse is(HfX₄/TMA/Ox)n₂ or (HfX₄/Ox/TMA)n₃.

In embodiments, said material of the second embodiment of the secondaspect may further comprise from 0 to 5 at % of hydrogen as determinedby Time-of-Flight Elastic Recoil detection analysis (TOF-ERDA).

In a third aspect, the present disclosure relates to a materialobtainable by the method according to any one embodiment of the firstaspect.

In a fourth aspect, the present disclosure relates to a devicecomprising a metal-insulator-metal stack, said stack comprising:

-   -   A first metal layer,    -   A layer of material according to any embodiment of the second or        third aspect,    -   A HfO₂ layer, and    -   A second metal layer.

In a further aspect, the present disclosure relates to a memory devicecomprising a metal-insulator-metal stack of layers, wherein saidinsulator comprises a layer of material according to any one of thesecond, third or fourth aspect.

In an embodiment, said memory device may be a resistive RAM

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure will be further elucidated by means of the followingdescription and the appended figures.

FIG. 1 is a graph showing the mass gain of the substrate (a 300 mmwafer) after 100 full HfCl₄/TMA cycles for a 4 s TMA pulse in functionof the HfCl₄ pulse length according to an embodiment of the presentdisclosure.

FIG. 2 is a graph showing the mass gain of the substrate (a 300 mmwafer) after 100 full HfCl₄/TMA cycles for a 3 s HfCl4 pulse in functionof the TMA pulse length according to an embodiment of the presentdisclosure.

FIG. 3 is a graph showing the evolution of the sheet resistance after100 full HfCl₄/TMA cycles for a 3 sec TMA pulse length in function ofthe HfCl₄ pulse length according to an embodiment of the presentdisclosure.

FIG. 4 is a graph showing the evolution of the sheet resistanceuniformity after 100 full HfCl₄/TMA cycles for a 3 sec TMA pulse lengthin function of the HfCl₄ pulse length according to an embodiment of thepresent disclosure.

FIG. 5 shows the temperature dependency of the growth per cycle HfCl₄ (4s)-purge-TMA (3 s)-purge according to an embodiment of the presentdisclosure.

FIG. 6 shows the temperature dependency of the film density according toan embodiment of the present disclosure wherein a pulse sequence HfCl₄(4 s)-purge-TMA (3 s)-purge is repeated until saturation.

FIG. 7 shows the temperature dependency of the growth per cycle HfCl₄ (5s)-purge-TMA (4 s)-purge-H₂O (1 s) according to an embodiment of thepresent disclosure.

FIG. 8 shows the temperature dependency of the film density according toan embodiment of the present disclosure wherein a pulse sequence HfCl₄(5 s)-purge-TMA (4 s)-purge-H₂O (1 s) is followed.

FIG. 9a shows the optical properties of a film produced according to anembodiment of the present disclosure wherein a pulse sequence HfCl₄ (5s)-purge-TMA (4 s)-purge-H₂O (1 s) is followed.

FIG. 9b shows the optical properties of a film produced according to anembodiment of the present disclosure wherein a pulse sequence HfCl₄ (5s)-purge-TMA (4 s)-purge-HfCl₄ (5 s)-purge-H₂O (1 s) is followed.

FIG. 10 shows the composition as determined by XPS for a materialaccording to the first embodiment of the second aspect of the presentdisclosure for a deposition temperature of 370° C.

FIG. 11 shows the composition as determined by XPS for a materialaccording to the second embodiment of the second aspect of the presentdisclosure for a deposition temperature of 370° C.

FIG. 12 shows the composition as determined by XPS for a materialaccording to the first embodiment of the second aspect of the presentdisclosure for a deposition temperature of 340° C.

FIG. 13 shows the composition as determined by XPS for a materialaccording to the first embodiment of the second aspect of the presentdisclosure for a deposition temperature of 370° C.

FIG. 14 is a schematic representation of a device according to anembodiment of the present disclosure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present disclosure will be described with respect to particularembodiments and with reference to certain drawings but the disclosure isnot limited thereto but only by the claims. The drawings described areonly schematic and are non-limiting. In the drawings, the size of someof the elements may be exaggerated and not drawn on scale forillustrative purposes. The dimensions and the relative dimensions do notnecessarily correspond to actual reductions to practice of thedisclosure.

Furthermore, the terms first, second, third and the like in thedescription and in the claims, are used for distinguishing betweensimilar elements and not necessarily for describing a sequential orchronological order. The terms are interchangeable under appropriatecircumstances and the embodiments of the disclosure can operate in othersequences than described or illustrated herein.

Moreover, the terms top, bottom, over, under and the like in thedescription and the claims are used for descriptive purposes and notnecessarily for describing relative positions. The terms so used areinterchangeable under appropriate circumstances and the embodiments ofthe disclosure described herein can operate in other orientations thandescribed or illustrated herein.

Furthermore, the various embodiments, although referred to as“preferred” are to be construed as exemplary manners in which thedisclosure may be implemented rather than as limiting the scope of thedisclosure.

The term “comprising”, used in the claims, should not be interpreted asbeing restricted to the elements or steps listed thereafter; it does notexclude other elements or steps. It needs to be interpreted asspecifying the presence of the stated features, integers, steps orcomponents as referred to, but does not preclude the presence oraddition of one or more other features, integers, steps or components,or groups thereof. Thus, the scope of the expression “a devicecomprising A and B” should not be limited to devices consisting only ofcomponents A and B, rather with respect to the present disclosure, theonly enumerated components of the device are A and B, and further theclaim should be interpreted as including equivalents of thosecomponents.

EXAMPLES

All depositing steps have been performed in an ASM Pulsar® 3000connected to a Polygon 8300.

The substrates were 300 mm Si (100) wafers having a 10 nm SiO2 top layergrown by rapid thermal oxidation.

The precursor HfCl₃ was purchased from ATMI and used as such.

Example 1 HfC Process

Adequate pulse length will vary in function of the used experimental setup, the optimal pulse length for the present experimental set up wastherefore determined experimentally.

First, mass gain (mg) on the substrate at 370° C. was measured infunction of HfCl₄ pulse length (ms) (FIG. 1). It was observed that massgain saturates at 11 mg for pulse lengths of 3 s or above.

Second, mass gain (mg) on the substrate at 370° C. was measured infunction of TMA pulse length (ms) (FIG. 2). It was observed that massgain increases slowly with TMA pulse length. This was indicative of asmall CVD component. Such CVD components get more dominant at highertemperature and are not favourable for ALD. This indicates that it isless advantageous to operate with a substrate above 370° C.

It is advantageous for the HFC material to be a bad dielectric or ametal. Sheet resistance and sheet resistance uniformity has thereforebeen measured for various HfCl₄ pulse lengths while keeping the TMApulse at 3 seconds. The following pulse sequence was therefore performedon a substrate at 370° C.: HfCl₄ (2-5 s)/N₂ purge/TMA (3 s)/N₂ purge. Ashorthand description of this same sequence is HfCl₄ (2-5 s)/TMA (3 s).

The corresponding graphs are shown in FIGS. 3 and 4 where RS stands forsheet resistance, RS U. stands for sheet resistance uniformity, and p.l.stands for pulse length. From these graphs it was observed that thelowest sheet resistance and the best uniformity was obtained for thefollowing pulse sequence: HfCl₄ (4 s)/TMA (3 s). The resistivity of theobtained layer was about 20 mOhm.cm.

The sequence HfCl₄ (4 s)/TMA (3 s) was repeated until saturation atdifferent temperatures in order to determine the temperature dependenceof the growth per cycle (G. p. c.) (see FIG. 5).

The thickness was measured by x-ray reflectivity. From FIG. 5, it isclear that the growth per cycle strongly increases above 300° C. and isbest around 370° C. This indicates a usable temperature window of from250° C. to 500° C. However, we know from FIG. 2 that it is lessadvantageous to operate with a substrate above 370° C., due to TMAdecomposition (CVD component). No reaction and therefore no materiallayer deposition were observed below 250° C.

The temperature dependency of the material layer density was measured byx-ray reflectivity (see FIG. 6) on the same samples used forestablishing FIG. 5. It can be seen in FIG. 6 that a higher density isobtained at higher temperatures. The density remains however relativelylow (4-5 g/cm³ when compared to the bulk density (12.2 g/cm³) of fullcrystalline HfC according to the literature.

The composition of the HfC material layer at various depths wasdetermined by alternating etching (via Ar sputtering) and XPS analysis.This has been performed at a deposition temperature of 300 (FIG. 13),340 (FIG. 12), and 370° C. (FIG. 10). Peaks characteristics of Hf, C,Al, Cl and O were found. At the deposition temperature of 370° C., thebulk concentration of C was from 41 to 44 at % as measured by XPS. Thebulk concentration of Hf was from 35 to 38 at % as measured by XPS. Thebulk concentration of Al was from 10 to 13 at % as measured by XPS. Thebulk concentration of O was from 4 to 5 at % as measured by XPS. Thebulk concentration of Cl was from 3 to 4 at % as measured by XPS. At thedeposition temperature of 340° C., the bulk concentration of C was from40 to 43 at % as measured by XPS. The bulk concentration of Hf was from33 to 37 at % as measured by XPS. The bulk concentration of Al was from9 to 12 at % as measured by XPS. The bulk concentration of O was from 6to 9 at % as measured by XPS. The bulk concentration of Cl was from 5 to7 at % as measured by XPS. At the deposition temperature of 300° C., thebulk concentration of C was from 32 to 38 at % as measured by XPS. Thebulk concentration of Hf was from 30 to 37 at % as measured by XPS. Thebulk concentration of Al was from 6 to 10 at % as measured by XPS. Thebulk concentration of O was from 7 to 14 at % as measured by XPS. Thebulk concentration of Cl was from 3 to 9 at % as measured by XPS.

At each of these temperatures, the presence of the oxygen is believed tobe due to the time the sample spent in the presence of air (30 min)before the XPS measurements. It can therefore in principle be reduced tozero.

Example 2 HfCO Process

The following pulse sequence was performed on a substrate at 370° C.:HfCl₄ (5 s)-N₂ purge-TMA (5 s)-N₂ purge-H₂O (1 s)-N₂ purge.

The sequence HfCl₄ (5 s)/TMA (5 s)/H₂O (1 s)/was repeated at differenttemperatures in order to determine the temperature dependence of thegrowth per cycle (G. p. c.) (see FIG. 7).

The thickness was measured by x-ray reflectivity. From FIG. 7, it isclear that the growth per cycle is best around 370° C. This suggests ausable temperature window of from 250° C. to 500° C. However, we knowfrom FIG. 2 that it is less advantageous to operate with a substrateabove 370° C., due to TMA decomposition (CVD component). No reaction andtherefore no material layer deposition were observed below 250° C.

The temperature dependency of the material layer density was measured byx-ray reflectivity (see FIG. 8). It can be seen in this figure that athe density decreases slowly between 300 and 370° C. The density remainshowever close to the expected bulk density. The expected bulk density isdetermined by an interpolation between bulk Al₂O₃ and HfO₂.

The composition of the HfCO material layer at various depths wasdetermined by alternating etching (via Ar sputtering) and XPS analysis.Peaks characteristics of Hf, C, Al, and O were found. The bulkconcentration of C was not determined because it was too close to thedetection limit. The bulk concentration of Hf was from 18 to 23 at %.The bulk concentration of Al was from 16 to 21 at %. The bulkconcentration of O was from 57 to 61 at %.

FIG. 9a shows the optical properties ((absorption*photon energy)² vs.photon energy) of the material obtained via a pulse sequence HfCl₄ (5s)-purge-TMA (4 s)-purge-H₂O (1 s)-purge.

The band gap can be calculated from the optical properties by a linearinterpolation of the square of the absorption coefficient to zero. Theseproperties show that the obtained material is a dielectric materialhaving a band gap of 6.3 eV.

FIG. 9b shows the optical properties (absorption*photon energy)² vs.photon energy) of a material obtained via a pulse sequence HfCl₄ (5s)-purge-TMA (4 s)-purge-HfCl₄ (5 s)-purge-H2O (1 s)-purge.

The band gap can be calculated from the optical properties by a linearinterpolation of the square of the absorption coefficient to zero. Theseproperties show that the obtained material is a dielectric materialhaving a band gap similar of 6.1 eV.

FIG. 14 shows a device according to the fourth aspect of the presentdisclosure. It shows a substrate (1) on which a metal-insulator-metalstack is deposited, said stack comprising:

-   -   A first metal layer (2),    -   A layer of material according to any embodiment of the second or        third aspect (3),    -   A HfO₂ layer (4), and    -   A second metal layer (5).

The invention claimed is:
 1. A method for the manufacture of a layer ofmaterial over a substrate, said method comprising: a) providing asubstrate, and b) depositing a layer of material on said substrate viaatomic layer deposition (ALD) at a temperature of from 250 to 500° C.,said depositing step comprising one or more deposition cycles, each saiddeposition cycle comprising: at least one HfX₄ pulse followed by apurge, and at least one trimethyl-aluminum (TMA) pulse followed by apurge, and a single oxidizer (Ox) pulse followed by a purge, wherein Xis a halogen selected from Cl, Br and I, and wherein a HfX₄ pulse-purgesequence of each said deposition cycle is performed immediately beforeor immediately after a TMA pulse-purge sequence.
 2. The method accordingto claim 1, wherein in each said deposition cycle, at least one of theHfX₄ pulse-purge sequences is immediately followed by one of the TMApulse-purge sequences.
 3. The method according to claim 1, wherein saidsingle Ox pulse is selected from H₂O and O₃ pulses.
 4. The methodaccording to claim 1, wherein each said deposition cycle comprises asequence of pulses HfX₄/TMA/Oxidizer/.
 5. The method according to claim1, further comprising a step of providing a HfO₂ layer over or undersaid layer of material.
 6. The method according to claim 5, wherein saidHfO₂ layer is provided by a sequence of m cycles of pulsesHfX₄/Oxidizer/, wherein m is from 1 to
 100. 7. The method according toclaim 1, wherein X is Cl.
 8. The method according to claim 1, whereinsaid temperature is from 300 to 400° C.
 9. The method according to claim1, wherein the layer of material comprises the elements Hf, Al, O, andoptionally C and X, wherein said elements Hf, Al, C, O and X make up atleast 90 atom percent (at %) composition of the layer of material asdetermined by XPS, and wherein Hf represents from 17 to 23% of the totalat % of said elements Hf, Al, C, O and X as measured by XPS; Alrepresents from 16 to 23% of the total at % of said elements Hf, Al, C,O and X as measured by XPS; O represents 57 to 62% of the total at % ofsaid elements Hf, Al, C, O and X as measured by XPS; C represents from 0to 3% of the total at % of said elements Hf, Al, C, O and X as measuredby XPS; and X represents from 0 to 1% of the total at % of said elementsHf, Al, C, O and X as measured by XPS.
 10. The method according to claim9, wherein the layer of material comprises hydrogen atoms in an amountof 0-5 at % as measured by time-of-flight elastic recoil detectionanalysis.
 11. The method according to claim 1, wherein each saiddeposition cycle consists of a HfX₄ pulse followed by a purge, a TMApulse followed by purge, and an Ox pulse followed by a purge.
 12. Themethod according to claim 1, wherein each said deposition cycle consistsof a sequence of pulses selected from the group consisting of:HfX₄/TMA/HfX₄/Oxidizer/, and HfX₄/TMA/Oxidizer/.
 13. The methodaccording to claim 1, wherein said depositing step comprises a pluralityof deposition cycles, each said deposition cycle comprising a sequenceof pulses HfX₄/Oxidizer/TMA/.